Yellowstone is the only place in the lower 48 states
where a population of wild bison has persisted since
prehistoric times, although fewer than 50 native bison
remained here in 1902. Fearing extinction, the park
imported 21 bison from two privately-owned herds, as
foundation stock for a bison ranching project that
spanned 50 years at the Buffalo Ranch in Yellowstone's
Lamar Valley. Activities there included irrigation,
hay-feeding, roundups, culling, and predator control,
to artificially ensure herd survival. By the 1920s,
some intermingling of the introduced and wild bison
had begun. With protection from poaching, the native
and transplanted populations increased. In 1936, bison
were transplanted to historic habitats in the Firehole
River and Hayden Valley. In 1954, the entire
population numbered 1,477. Bison were trapped and
herds periodically reduced until 1967, when only 397
bison were counted parkwide. All bison herd reduction
activities were phased out after 1966, again allowing
natural ecological processes to determine bison
numbers and distribution. Although winterkill takes a
toll, by 1996 bison numbers had increased to about 3,500.
Bison are nomadic grazers, wandering high on
Yellowstone’s grassy plateaus in summer. Despite their
slow gait, bison are surprisingly fast for animals
that weigh more than half a ton. In winter, they use
their large heads like a plow to push aside snow and
find winter food. In the park interior where snows are
deep, they winter in thermally influenced areas and
around the geyser basins. Bison also move to winter
range in the northern part of Yellowstone.
Bison are enjoyed by visitors, celebrated by
conservationists, and revered by Native Americans. Why
are they a management challenge? One reason is that
about half of Yellowstone's bison have been exposed to
brucellosis, a bacterial disease that came to this
continent with European cattle and may cause cattle to
miscarry. The disease has little effect on park bison
and has never been transmitted from wild bison to a
visitor or to domestic livestock. Despite the very low
risk to humans and livestock today, since the
possibility of contagion exists, the State of Montana
believes its "brucellosis-free" status may be
jeopardized if bison are in proximity to cattle.
Although the risk is very low, if cattle become
infected, ranchers can be prevented from shipping
livestock out of state until stringent testing and
quarantine requirements are met. Although scientists
are studying new possibilities, there is yet no known
safe, effective brucellosis vaccine for bison.
Ironically, elk in the ecosystem also carry the
disease, but this popular game species is not
considered a threat to livestock
Yellowstone wildlife freely move across boundaries set
a century ago without knowledge of each animal’s
habitat needs. But bison are not always unwelcome
outside the park. In the park managers have tried to
limit bison use of lands outside the park through
public hunting, hazing bison back inside park
boundaries, capture, testing for exposure to
brucellosis, and shipping them to slaughter. Since
1990, state and federal agency personnel have shot
bison that leave the park. During the severe winter of
1996-1997, nearly 1,100 bison were sent to slaughter.
The carcasses sold at public auction, or shot and
given to Native Americans. These actions reduced the
bison population to about 2,200 in 1997-1998. In the
mild winter of 1997-1998, only 11 bison were killed in
management actions, all in January, and all from the
West Yellowstone area. Six bison were shot and five
were sent to slaughter. Through the winter another 21
bison are known to have died, 12 of natural causes,
and 9 from other causes such as collisions with vehicles.
The NPS, U.S.D.A. Forest Service, U.S.D.A. Animal and
Plant Health Inspection Service, and the State of
Montana completed a Draft Environmental Impact
Statement for the Interagency Bison Management Plan
for the State of Montana and Yellowstone National Park
for public release on June 12, 1998. The purpose is to
maintain a wild free-ranging bison population and to
address the risk of brucellosis transmissions to
protect the economic interest and viability of the
livestock industry in Montana. Alternatives being
considered range from: allowing bison to freely range
over a large portion of public land inside and outside
the park; managing bison like elk and other wildlife
through controlled hunting outside park boundaries;
and attempting to eradicate brucellosis by capturing,
testing, and slaughtering infected bison at numerous
facilities constructed inside the park. Additional
options include purchase of additional winter range;
attacking brucellosis with a (yet unknown) safe and
effective vaccine for bison; and quarantine of animals
at appropriate locations such as Indian Reservations
or other suitable sites outside Yellowstone.
For more information on the Bison please see
YellowStone National Park Site
Click on "Nature" then "Yellowstone Wildlife pages" then "Bison"
|
